Modern sport and commercial diving has its roots in antiquity with the earliest referenced practice of diving occuring in the Iliad. Pearl and sponge diving and salvage operations have been engaged in since Greek and Roman times. Early divers were sometimes provided with devices for drawing air from above the water such as through a tube, one end of which would be carried in the mouth while the other end was made to float on the surface. In 17th century England, rudamentary diving bells were developed. When a container is immersed in water, with its opening pointing downward, the volume of air enclosed in it diminishes in proportion to its depth in the water, the air pressure being balanced by the pressure of the water at its own level. If, however, air is compressed in a container at a pressure slightly above the already existing pressure, the level of the water inside will drop until the air escapes from the lower rim of the vessel. This principle of the diving bell was applied in industry for laying bridge foundations. Greater mobility for the submerged diver has been provided in more recent times with the advent of the self-contained underwater breathing apparatus (scuba), wherein tanks of compressed air are worn on the diver's back and, when combined with a diving mask, a weighted belt and a means of propulsion, enabled men to swim and explore under water with greater freedom. Apparatus designed by J. Y. Costeau and E. A. Ghenan which provide a demand valve regulator for supplying air to the diver only on inhalation, have come into common usage.
The scuba diver, however, has a limited diving time of approximately one hour, the duration of which depends on the average depth of his dive, and this limits the distances over which he can explore while submerged. The prior art has attempted to take advantage of the freedom of scuba diving while, at the same time extending the exploration range while submerged, by providing various types of underwater cruising devices. The bathyscaph first constructed by Piccard and Cosyns in 1948, was a sealed steel cabin equipped with Plexiglas observation protholes, and was a self-contained submarine vessel equipped with its own means of propulsion. The principal application of a bathyscaph is for relatively deep diving at depth in excess of 1,000 feet. However most sport and commercial diving is done at depths of from 30 to 100 feet where there is no need for expensive, complex apparatus represented by the bathyscaph. The prior art has developed shallow immersion underwater cruise devices such as that disclosed in U.S. Pat. No. 3,400,680 which discloses a catamaran for underwater exploration. That patent describes a chair connected by a solid vertical pole to a suspension bridge mounted between a pair of pontoons of a catamaran vessel. In its upward position, the chair remains partially submerged in the water while the diver enters from the catamaran vessel. In its fully submerged position, the diver breathes from an air supply through a mouthpiece while carrying on his observations through a conventional skin diving face mask worn on his person. The chair can never be fully withdrawn from the water and therefor the vehicle cannot be readily transported by surface cruising from one diving station to another. The diving chair in that patent provides room for only a single occupant, which controverts the safety practice of two-man diving operations. In addition, since the diver seated in the diving chair described in that patent must wear a diving mask and air mouth-piece on his person, there is no relief from the pressure of the face mask or mouthpiece during the course of a lengthy exploration and no opportunity for oral communication with another diver. Another drawback is exposure of the diver's person to floating and suspended debris in the water while engaging in an underwater cruise operation. Furthermore, that patent describes a selective buoyancy technique employing an air ballast, to raise the diving chair, which requires the interruption of the breathing air supply, while the ballast tanks are filled for the ascent of the chair. The prior art has failed to provide an underwater cruise device suitable for sport and commercial diving which provides protection, convenience and long exploration range to the scuba diver.